1. Field of the Invention
The invention relates to an auto-aspirating, rotational dispersion device for gases and liquids, with a rotating hollow shaft for gas suction. In particular, the invention relates to a self-priming two-phase turbine for mixing together gases and liquids.
2. Description of the Prior Art
In conventional dispersion devices or self-priming two-phase turbines of the type indicated above, gas suction occurs through the rotating hollow shaft and liquid is also introduced into the inner chamber of the turbine, with the result that the gas and liquid are mixed together inside the turbine chamber. This kind of auto-aspirating two-phase turbine works satisfactorily with a gas/liquid phase ratio of up to about 25/30%. At larger phase ratios the auto-aspirating two-phase turbine becomes flooded and even when the rpm is increased an increase in performance is impossible, since the aspirated quantity of gas remains at rest and an increased mass transfer is not possible. For this reason the conventional, self-priming two-phase turbine in its very design is restricted by the predetermined gas/liquid phase ratio with respect to the mass transfer.
The object of the invention, therefore, is to create a high performance, auto-aspirating dispersion device for gases and liquids, or as the case may be, a two-phase turbine, which device eliminates the described difficulties while permitting a greater mass transfer under the most favorable possible conditions for performance and the rpm of the dispersion device.
To this end, the invention provides for an auto-aspirating, rotational dispersion device for gases and liquids with a rotating hollow shaft employed for gas suction, which device is distinguished by the fact that the gas being dispersed flows in a manner separate from the liquid, from the hollow shaft over gas channels communicating with said hollow shaft to openings in the gas channels that are positioned at intervals over the circumference, at which openings the gas and liquid are mixed outside of the dispersion device.
In the auto-aspirating, rotational dispersion device according to the invention, a plurality of gas channels are therefore connected to the hollow shaft; the gas being dispersed is thereby provided with an outlet through openings in the gas channels. The separation of flow creates a negative pressure at the gas channel openings which allows the gas to be aspirated from the gas chamber, against the static liquid head, through the dispersion device. The dispersion device according to the invention thereby assures continuous gas suction independent of the gas/liquid phase ratio, as based on the stall phenomenon at the gas channel opening. In the dispersion device according to the invention, moreover, the gas and liquid are mixed outside of the inner chamber of the dispersion device, specifically, in the area of the gas channel openings, since the gas channels provided by the inventive device conduct gas, but not liquid. When the dispersion device rotates, the gas channels produce intensive liquid transport, movement, and circulation, so that a high mass transfer is achieved by the intensive contact between the moving liquid and the aspirated and dispersed gas.
The separate guidance of the dispersed gas within the auto-aspirating dispersion device according to the invention thus assures that the device is not restricted by the predetermined gas/liquid phase ratios. The invention thereby provides an extremely capable auto-aspirating rotational dispersion device, or auto-aspirating two-phase turbine, providing a high mass transfer.
The performance of this kind of auto-aspirating dispersion device can be enhanced and its effectiveness improved by the appropriate design of its gas channels. Numerous possibilities are available here.
In one embodiment the gas channels run in roughly radial fashion relative to the hollow shaft. As an alternative, the gas channels can run at an acute angle to the radius, preferably in a range between 0 and 25xc2x0, particularly about 15xc2x0.
Furthermore, the gas channels can be designed in the form of agitator blades, to further intensify the liquid transport.
In the auto-aspirating, rotational dispersion device according to the invention, the gas channels will preferably have a curved design, so as to have a profile favorable to the material flow and one that promotes intensive liquid transport. The curvature radius can lie in a range from D2/3 to 3D2, but will preferably be about D2/2. D2 indicates the maximum diameter of the dispersion device, as measured from the outer edges of two opposite gas channel openings.
In particular, the gas channels can exhibit a cross-section that increases in size as it moves outward from the hollow shaft to the gas channel opening. This intensifies the suction of gas from the gas compartment, as based on the separation-of-flow phenomenon and the resulting negative pressure in the gas channel system.
In particular, the cross-section of each gas channel opening lies on a plane running at an acute angle to the gas channel wall; the angle will ideally lie in a range from 30xc2x0 to 60xc2x0, and more specifically will amount to 50xc2x0. This allows the mass transfer to be further improved due to the increased contact areas.
According to a preferred embodiment of the auto-aspirating, rotational dispersion device, the gas channels are positioned at regular angular distances over the circumference, so as to guarantee as uniform as possible a mixture of gas and liquid in the circumferential direction.
According to another embodiment of the auto-aspirating, rotational dispersion device according to the invention, cover disks are provided above and below the gas channels; the cover disks are spaced in axial fashion relative to the rotating hollow shaft and form compartments in conjunction with the gas channels. The lower cover disk can form a closed area which is connected to the hollow shaft. Together with the outer surface of the hollow shaft the upper cover disk will ideally form a gap for the suction of liquid. Liquid is drawn through this suction gap into the compartments formed by the two axially spaced cover disks and the outer surfaces of the gas channels; intensive agitation is imparted to the liquid to intensify the mass transfer.
The gas channel openings will preferably be oriented counter to the rotating direction of the hollow shaft, so that there is intensive intermixture of gas and liquid in the area of the gas channels facing away from the flow.
The invention will now be explained in greater detail on the basis of preferred embodiments, with reference to the attached drawing. Shown are:
FIG. 1 a schematic perspective view of an initial embodiment of an auto-aspirating, rotational dispersion device or an auto-aspirating two-phase turbine according to the invention
FIG. 2 a schematic top view of a variant of a dispersion device according to the invention
FIG. 3 a schematic top view of a further variant of a dispersion device according to the invention
FIG. 4 a schematic top view of another embodiment of a dispersion device according to the invention